Windshield wipers, especially of vehicles, conventionally receive linear motion only, and thus they conventionally do not include a brush. The brush is not simple, since it must be carried on the windshield wiper, thus it must be lightweight.
The simple solution for providing rotational movement is adding a motor. However, this makes the accessory heavy.
An additional solution is converting the linear motion of the windshield wiper to torque. However, the linear motion mechanism already is a relatively sensitive mechanism, and thus is not sufficient for supporting another mechanism.